Power generation systems have been designed for applications, such as in aircraft, where a generator develops electrical power from motive power supplied by an aircraft jet engine. In order to operate at temperatures at or below a first maximum temperature, such a system circulates cooling oil in passages in the rotor and stator of the generator and delivers the oil to a heat exchanger that receives cooling fluid in the form of ram air.
In such aircraft power generation systems, the generator is typically of the synchronous type and thus develops variable-frequency power owing to the variable-speed motive power supplied by the aircraft jet engine. The variable-frequency power must be converted to fixed-frequency power by a power converter before such power can be used by loads on-board the aircraft. Such power converters utilize high power semiconductor switching devices which generate substantial amounts of heat and which must be operated at or below a second maximum operating temperature. Often, the maximum operating temperature of the electrical components of the power converter is less than the maximum operating temperature of the generator. Thus, if the same cooling system is to be used to cool the power converter components and the generator, the system must be oversized with respect to the cooling requirements imposed by the generator. Otherwise, different cooling systems must be used for the power converter and generator, thereby undesirably increasing the size and weight of the overall power generation system.
Banthin, et al., U.S. Pat. No. 3,623,546 discloses a cooling system for an electronic assembly mounted on a gas turbine engine. Electronic equipment is placed in a thermally conductive fluid within an annular container which is in turn mounted about a fuel line. The container is double-walled and coolant air is directed through a space between the walls. Cooling is accomplished by the coolant air and the engine fuel and efficiency is said to be improved by the fluid in the annular container.
Wiedemann, U.S. Pat. No. 3,089,969 discloses a cooling arrangement for a turbogenerator wherein an oil pump supplies cooling oil to a stator of the turbogenerator while hydrogen is supplied as a cooling fluid to a rotor of the turbogenerator.
Richardson, et al., U.S. Pat. No. 3,487,242 discloses a cooling system for a rotor of a dynamoelectric machine.
Wellborn, et al., U.S. Pat. No. 3,015,222 and Richardson, et al., U.S. Pat. No. 3,407,623 disclose cooling apparatus for refrigeration components.